Get current user identity, context, available contexts, and effective permissions

Example response

{
  "success": true,
  "data": {
    "id": "550e8400-e29b-41d4-a716-446655440000",
    "email": "user@example.com",
    "first_name": "John",
    "last_name": "Doe",
    "current_context": {
      "id": "550e8400-e29b-41d4-a716-446655440000",
      "name": "Acme Corp"
    },
    "available_contexts": [
      {
        "id": "550e8400-e29b-41d4-a716-446655440000",
        "name": "Acme Corp",
        "roles": [
          "admin"
        ]
      }
    ],
    "effective_roles": [
      "partner:admin:550e8400-e29b-41d4-a716-446655440000"
    ],
    "permissions": [
      "merchants:list"
    ]
  }
}